Collective coupling of randomly dispersed oscillators with cavities filled with zero-index metamaterials Xiaohu Xu, Haitao Jiang, Yong Sun, Wenxing Liu, Yunhui Li and Hong Chen Eur. Phys. J. B, 87 2 (2014) 44 Published online: 26 February 2014 DOI: 10.1140/epjb/e2014-41061-2